To specify the influence of methods used in estimating area under the curve (AUC) and the meaning of total and incremental AUC, 75 glycemic responses to a mixed meal were studied in 75 diabetic patients, 39 with insulin-dependent diabetes mellitus and 36 with non-insulin-dependent diabetes mellitus. AUC was integrated with five computerized methods: polynomial interpolation of third and fourth degree, trapezoidal rule, Simpson's integration, and cubic interpolatory splines. Although these methods gave significantly different results (P less than 0.001), a strong correlation was found between estimations of AUC with different methods (r greater than 0.99, P less than 0.001). In addition, variation between methods was less than or equal to 2%, whereas the coefficient of variation between subjects was 38%. Total AUC was strongly correlated with basal blood glucose value (r = 0.90, P less than 0.001), whereas incremental and positive AUC were not (r = 0.12 and 0.07, respectively, NS). Incremental and positive AUC were strongly correlated with glycemic rise (r = 0.89 and 0.93, respectively, P less than 0.001), whereas total AUC was only slightly so (r = 0.31, P less than 0.01). Incremental and positive AUC gave slightly but significantly different information on glucose response. These results suggest that variations related to the method used in estimating AUC are not clinically relevant and that a simple method such as trapezoidal rule can be used. Total AUC is a descriptive factor related to basal blood glucose value, whereas incremental and positive AUC more accurately describe glycemic response to foods.

These results suggest that glucose and insulin responses to a test meal are reproducible in type II diabetic patients.

In order to study the influence of non-carbohydrate foods on responses to carbohydrates during mixed meals, 30 Type 2 (non-insulin-dependent) diabetic patients followed a standardized diet for 5 consecutive days. On days 2, 3, 4, and 5, four different lunches were eaten in a randomized order. Lunches consisted of rice or glucose (50 g carbohydrate) eaten either alone, or as part of a mixed meal (32 g protein, 20 g fat). Glucose and insulin levels prior to the lunches did not differ significantly. Glucose and insulin responses differed (p less than 0.001), responses to rice being lower than responses to glucose, and responses to the meal plus rice lower than responses to the meal plus glucose. The ratios of glucose responses to rice and glucose (glycaemic index) were similar (alone, 47 +/- 4%; meal, 47 +/- 4%; NS). The ratios of the insulin responses did not differ (78 +/- 8 vs 96 +/- 7%; NS). The blood glucose responses to mixed meals were lower than responses to the carbohydrates eaten alone, the ratios being similar (rice, 52 +/- 3%; glucose, 58 +/- 5%; NS). Serum insulin responses were however higher, and the ratios differed (172 +/- 13 vs 138 +/- 14%; p = 0.05). These results suggest that the glycaemic index of isolated carbohydrate foods can predict the relative response to mixed meals in the same individuals with Type 2 diabetes. They also support the insulin secretagogue effect of non-carbohydrate foods, which may vary according to the source of carbohydrate in the meal.